This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Plastic capillaries of identical size produced from six different clear grades of polymers were tested to determine which polymer produces the smallest x-ray background and is the most suitable for the production of sample containers used for protein crystallography x-ray diffraction data collection at cryogenic temperatures. The polymers tested were: Acrylonitrile butadiene styrene (ABS), Polymethyl methacrylate (Acrylic), Polyamide (PA), High Impact Polystyrene (HIP), Polycarbonate (PC), and Low Density Polyethylene (LPDE). Data were collected on SSRL BL7-1. Each sample was exposed to 0.976 A x-rays for about 30 seconds at a temperature of 100 K. The incident intensity was monitored and the exposure time varied to ensure each sample received an equivalent x-ray dose. Care was taken to expose the same volume of plastic from each sample tested. Each plastic was rotated five degrees during the exposure. The scattered intensity was measured by a Q315 CCD detector located at a distance of 251 mm from the sample giving a maximum resolution of 1.37 A. The optical properties of each of the plastic containers were also assessed. This work was done in collaboration with researchers at the Hauptman Woodward Medical Research Institute with the goal of developing a small plastic capillary that can be used both for crystal growth and x-ray diffraction quality screening. The capillary will be used as a pipette tip with both manual pipetters and automated liquid handling robots enabling solutions for crystal growth to be easily drawn inside. For x-ray data collection, the larger end of the capillaries fits onto a metal base and the assembly fits inside the SSRL cassette or uni-puck sample storage container and is compatible with the SSRL automated sample mounting system for automated screening and remote access data collection.